Boil the potatoes and sweet potato separately until soft - about 25 minutes each.
Meanwhile boil the chestnuts for 20 minutes in the stock.
Sauté the rosemary, remaining vegetables, dates, yeast extract and tomatoes in the olive oil. Add this to the chestnuts and their juice (which should be mostly soaked up by now) and simmer for about 15 - 20 minutes.
Heat the soya milk then using a hand-blender (rather than a whisk) blend it with the oil. Once the oil and soya milk are blended, blend in the lime juice (to emulsify the oil and soya milk).
Drain the potatoes and mash them with 3 tablespoons soya milk mixture, parsley and some salt and pepper.
Blend the remaining soya milk mixture with mustard, bouillon mix, and the garlic clove.
Mix together the balsamic vinegar, black strap molasses, carob powder, corn flour, tomato puree, and orange juice to make a paste. Add to the chestnuts and vegetables whilst stirring over a low heat until the sauce thickens.
Divide the mixture into six 12 cm / 4 - 5 pots then cover with a layer of mashed potato, and finally top with the 'cheesy' sauce.
Place in a preheated oven 180°C (350°F) Gas Mark 4 for about 20 minutes until the topping goes bubbly and golden.
Alternatively make 6 stacks of the potato coated with the sauce and grill them for 10 minutes to serve separately with the hot stew.